Table 2 Likelihood ratios (LR) for disease duration, C-reactive protein (CRP) levels and Berlin MRI score in predicting a Bath Ankylosing Spondylitis Disease Activity Index 50% improvement (BASDAI 50) response in patients with active ankylosing spondylitis (AS)
ParameterPatients (n) with BASDAI 50 responsePatients (n) without BASDAI 50 responseLR*
Disease duration:
    ⩾20 years4120.28
    10–19 years660.84
    <10 years1534.20
CRP (mg/litre):
    <6390.28
    6–24.91071.20
    25–39.9431.12
    ⩾40823.37
Berlin MRI spine score:
    0480.42
    1–41071.43
    5–10350.50
    ⩾11816.67
Total†2521

  • *LR = likelihood ratio, defined as sensitivity/(100-specificity). †The total population (n = 46) comprises patients with AS for whom MRI of the spine prior to anti-TNF treatment was available.

  • TNF, tumour necrosis factor.